This invention relates to a method for recording and reproducing an optical recording medium, and more specifically to a method for recording information on an optical recording medium, reproducing the information or erasing the information by utilizing plasma resonance absorption which takes place in the recording film of the optical recording medium upon illumination of light thereto.
Since fine grains of certain inorganic materials are equipped with such characteristics that they have high chemical reactivity, permit poor thermal diffusion and hence tend to induce concentration of heat, and are equipped with high light absorption indices, there have been proposed highly-sensitive optical recording media in each of which these fine grains are fixed as a film on a substrate. For example, Japanese Unexamined Patent Publication No. 94944/1982 discloses a method for recording and reproducing information by forming a thin recording film, which contains fine grains of various inorganic materials in a dispersed state, on a substrate and then illuminating the thin recording film with a light beam such as laser beam or electron beam so as to form, in the thin recording film, spots changed in structure, quality or color.
On the other hand, Japanese Unexamined Patent Publication No. 74392/1983 discloses a method for illuminating an isle-like cohesive film of fine grains of a metal or sub-metal with a laser beam, whereby the illuminated spots are caused to fuse or evaporate to form sunk pits there.
In the above-mentioned optical recording media, the fine grains or the recording films which contain such fine grains undergo irreversible changes upon their recording. Once information has been recorded by illumination of light, it will be impossible to erase the thus-recorded information. In other words, such conventional optical recording media are thus accompanied by a problem that they do not permit repeated utilization.